The most common approach for providing hot water in both domestic and commercial settings involves the use of large tanks for the storage of hot water. Although such heated tank systems can provide hot water at a relatively high flow rate, they are inherently energy inefficient because the water in the tank is continually reheated even when water is not being used on a regular basis.
Another approach to providing hot water involves the use of a tankless water heater system that heats water only when water is being used. Such tankless water heater systems, also referred to as demand water heater systems, can often provide a more energy efficient means of heating water than storage systems using the same type of heating (e.g., gas, electric, etc.). However, one common draw back of traditional tankless water heater systems is their inability to provide hot water at high flow rates. Typically, traditional tankless water heater systems have difficulty providing domestic hot water (e.g. for shower water with a temperature typically of about 90-100° F. (32-38° C.)) at flow rates greater than about 6 gallons per minute (22.7 liters per minute). These difficulties can be even more pronounced in industrial settings where process hot water is typically water with a temperature of about 140° F. (60° C.) or higher.
There are many uses to which a tankless hot water system capable of delivering hot water at flow rates above 6 gallons per minute (GPM) could be applied. In addition to uses as more energy efficient domestic and industrial hot water supplies, tankless hot water systems with sufficient flow rates could be used to provide hot water for portable, semi-portable or fixed decontamination showers. A heated decontamination shower could prove very useful in situations requiring outdoor decontamination on cold days, for example, in the event of a chemical, biological, and/or nuclear (dirty-bomb) terrorist attack in winter on a Canadian, northern U.S., Russian or northern European city.
A need therefore continues to exist for hot water delivery systems that can provide hot water in a more energy efficient manner than storage tank systems yet still deliver hot water at the higher flow rates associated with storage tank systems.